Method for making a multilayered golf ball

ABSTRACT

The invention provides a method for making a golf ball. Two cups are molded from an elastomer separately from an inner sphere. In one embodiment of the method, the cups are molded on both sides of a single mold part with hemispherical protrusions that form cavities in the cups. An inner sphere is placed within the cavities, and the cups are joined, by preferably crosslinking the cups together or applying adhesive there between. To retain the characteristics of the cup material where the cups meet, an embodiment of the cups can be formed with nonplanar mating surfaces that mesh with each other. The nonplanar mating surfaces preferably have a pattern that is symmetrical about the inner sphere, such as concentric ridges, for example a tongue and a groove.

This is a divisional of application Ser. No. 09/312,480, filed on May17, 1999, which is a continuation of application Ser. No. 08/902,351,filed on Jul. 29, 1997 now abandoned, which is a continuation-in-partapplication of U.S. application Ser. No. 08/615,346, which was filed onMar. 11, 1996, and is now U.S. Pat. No. 5,683,312. These applicationsand patent are expressly incorporated by reference herein in theirentirety.

FIELD OF THE INVENTION

The present invention is directed to a method for making a golf ball.More particularly, the invention is directed to a method for making amultilayered golf ball having a plurality of core parts or cups arrangedaround a center and bound to each other by crosslinking or an adhesive.

BACKGROUND OF THE INVENTION

Generally, golf balls have been classified as two piece balls or threepiece balls. Two piece balls are comprised of a solid polymeric core anda cover. These balls are generally easy to manufacture, but are regardedas having limited playing characteristics. Three piece balls arecomprised of a solid or liquid-filled center surrounded by tensionedelastomeric material and a cover. Three piece balls generally have agood “click” and “feel” when struck by a golf club, but are moredifficult to manufacture than two piece balls.

The prior art is comprised of various golf balls that have been designedto provide optimal playing characteristics. These characteristics aregenerally the initial velocity and spin of the golf ball, which can beoptimized for various players. For instance, certain players prefer toplay a ball that has a high spin rate for playability. Other playersprefer to play a ball that has a low spin rate to maximize distance.However, these balls tend to be hard feeling and difficult to controlaround the greens.

The prior art is comprised of liquid filled golf balls. Wound golf ballshave been made with liquid filled centers for many years. Both U.S. Pat.Nos. 1,568,513 and 1,904,012 are directed to wound golf balls withliquid filled centers. U.S. Pat. Nos. 5,150,906 and 5,480,155, aredirected to a hollow spherical shell of a polymeric material which isfilled with a liquid or unitary, non-cellular material that is a liquidwhen introduced into the shell. The shell is disclosed as being theouter cover or an inner layer with the outer cover formed to theexternal surface thereof. The shell varies in thickness from about 0.060to 0.410 inches in thickness.

Other known attempts to mold layers around a solid center entail placinga preformed center between two blocks of core material in a sphericalcompression mold, and closing the mold. This is done in the manufactureof golf balls sold by Kamatari. This process, however, provides littlecontrol over the ultimate placement of the center within the golf ballcore. Large variations in center eccentricities can result.

The prior art also provides for the manufacture of double cover golfballs. This is generally accomplished by injection molding a first andthen a second cover layer around a core. This system, however, requirescomplex injection molds, usually with retractable pins within the moldto properly position the core.

SUMMARY OF THE INVENTION

The invention provides a method for making a golf ball, particularlysuited for golf balls that have a multilayer core with a fluid center,and also a golf ball resulting from the inventive process. The methodcomprises forming a solid or fluid filled inner sphere, and thenseparately molding from elastomeric material, preferably polybutadiene,core parts, such as hemispherical cups. When the cups are combined ahollow sphere is formed.

The each hemispherical cup has a hemispherical cavity, produced by aprotrusion of a mold part. The inner sphere is placed between two cups,which are then joined to form a liquid center shell of the core. Whenthe cups are joined, the hemispherical cavities together form aspherical cavity, now occupied by the inner sphere, and the cupsthemselves form a liquid center shell of the core. Thus, the innersphere is easily positioned concentrically within the finished ball.Finally, a cover is molded around the core. This process results inaccurate and repeatable central placement of the inner sphere within thecore.

The process is not susceptible to unwanted deformation of a soft innersphere during placement within the cup' cavities because the method doesnot depend on the rigidity of the inner sphere in the shaping of thecups. Moreover, as the cups are molded separately from the inner sphere,the process avoids deforming a soft inner sphere containing a fluidbecause compressing the cup material about the inner sphere is notrequired.

In a method according to the invention, the two cups are molded on bothsides of a single protrusive mold part that has a hemisphericalprotrusion on each side for forming each hemispherical cavity.

Once the cups are formed, they are joined by applying an adhesivebetween them and pressing them together. The adhesive employed also hasan adhesive strength that is preferably stronger than the cohesivestrength of the elastomeric core material. The adhesive is preferablyflexible in its cured state.

An alternative method to employing adhesive is to join the cups bypressing them together while their temperature is elevated to crosslinkthe material from one cup to the other.

The invention also provides making hemispherical cups with nonplanarmating surfaces. The mating surfaces are substantially flat in oneembodiment, but, in another embodiment, define a pattern that issymmetrical about the inner sphere, such as of concentric ridges thatmesh when the two cups are joined. These ridges may comprise acorresponding tongue and groove. The nonplanar surfaces improve theshear strength of the finished ball where the cups are joined and retainmore characteristics of the cup material throughout the joining regionthan do balls with flat mating surfaces.

Properties of golf balls according to the invention, such as spin rate,spin decay, compression, and initial velocity, may be varied, forexample by selecting appropriate specific gravities and viscosities of afluid in the inner sphere. The fluid may have a high specific gravityand low viscosity for a high spin ball or a low specific gravity andhigh viscosity for a low spin ball. The properties of the liquid centershell or one or more mantle layers in the ball, such as specificgravity, resiliency, and compression can also be varied to make ballshaving the desired characteristics.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view of a ball of the present invention;

FIG. 2 is a sectional view of a ball according to the present inventionwith the liquid center shell and multiple mantle and cover layers aroundan inner sphere;

FIG. 3 is a sectional view of a mold performing a single cup;

FIG. 4 is a sectional view of molds preforming a mantle layer's cupsaccording to the present invention;

FIG. 5 is a sectional view of molds joining cups of a golf ball mantlelayer;

FIG. 6 is a sectional view of the mold joining cups of a golf ballmantle layer around an inner sphere of frozen fluid;

FIG. 7 is a sectional view of a ball according to the invention havingadhesive joining the cups;

FIG. 8 illustrates a compression mold forming a cover around a golf ballcore;

FIG. 9 shows an injection mold forming a cover around a core; and

FIGS. 10 and 11 are sectional views of cups with nonplanar matingsurfaces that mesh with one another.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, ball 10 includes a cover 11 and a core 12. The core12 has an inner sphere 13 that is disposed concentrically therein andwhich comprises a fluid center 18 in a cavity within a liquid centershell 20. The core 12 also has a first mantle layer 22, which surroundsthe inner sphere 13. Together, the liquid center shell 20 and the firstmantle layer 22 are part of a mantle portion 16 of the ball. The mantleportion 16 of FIG. 2 has an additional second mantle layer 40. Theliquid center shell 20 and mantle layers 22 and 40 are preferablyelastomers.

The cover 11 provides the interface between the ball 10 and a club andother objects such as trees, cart paths, and grass. Properties that aredesirable for the cover are good flowability, high abrasion resistance,high tear strength, high resilience, and good mold release, amongothers.

The cover 11 can be comprised of polymeric materials such as ioniccopolymers of ethylene and an unsaturated monocarboxylic acid which areavailable under the trademark “SURLYN” of E.I. DuPont De Nemours &Company of Wilmington, Del. or “IOTEK” or “ESCOR” from Exxon. These arecopolymers of ethylene and methacrylic acid or acrylic acid partiallyneutralized with zinc, sodium, lithium, magnesium, potassium, calcium,manganese, nickel or the like.

In accordance with the various embodiments of the present invention, thecover 11 has a thickness to generally provide sufficient strength, goodperformance characteristics and durability. Preferably, the cover 11 isof a thickness from about 0.03 inches to about 0.12 inches. Morepreferably, the cover 11 is about 0.04 to 0.09 inches in thickness and,most preferably, is about 0.05 to 0.085 inches in thickness.

In accordance with a preferred embodiment of this invention, the cover11 can be formed from mixtures or blends of zinc, lithium and/or sodiumionic copolymers.

The Surlyn® resins for use in the cover 11 are ionic copolymers in whichsodium, lithium or zinc salts are the reaction product of an olefinhaving from 2 to 8 carbon atoms and an unsaturated monocarboxylic acidhaving 3 to 8 carbon atoms. The carboxylic acid groups of the copolymermay be totally or partially neutralized and might include methacrylic,crotonic, maleic, fumaric or itaconic acid.

This invention can likewise be used in conjunction with homopolymericand copolymer materials such as:

(1) Vinyl resins such as those formed by the polymerization of vinylchloride, or by the copolymerization of vinyl chloride with vinylacetate, acrylic esters or vinylidene chloride.

(2) Polyolefins such as polyethylene, polypropylene, polybutylene andcopolymers such as ethylene methylacrylate, ethylene ethylacrylate,ethylene vinyl acetate, ethylene methacrylic or ethylene acrylic acid orpropylene acrylic acid and copolymers and homopolymers produced usingsingle-site catalyst.

(3) Polyurethanes such as those prepared from polyols and diisocyanatesor polyisocyanates and those disclosed in U.S. Pat. No. 5,334,673.

(4) Polyureas such as those disclosed in U.S. Pat. No. 5,484,870.

(5) Polyamides such as poly(hexamethylene adipamide) and others preparedfrom diamines and dibasic acids, as well as those from amino acids suchas poly(caprolactam), and blends of polyamides with Surlyn,polyethylene, ethylene copolymers, ethyl-propylene-non-conjugated dieneterpolymer, etc.

(6) Acrylic resins and blends of these resins with poly vinyl chloride,elastomers, etc.

(7) Thermoplastics such as the urethanes, olefinic thermoplastic rubberssuch as blends of polyolefins with ethylene-propylene-non-conjugateddiene terpolymer, block copolymers of styrene and butadiene, isoprene orethylene-butylene rubber, or copoly(ether-amide), such as PEBAX sold byELF Atochem.

(7) Polyphenylene oxide resins, or blends of polyphenylene oxide withhigh impact polystyrene as sold under the trademark “Noryl” by GeneralElectric Company, Pittsfield, Mass.

(8) Thermoplastic polyesters, such as polyethylene terephthalate,polybutylene terephthalate, polyethylene terephthalate/glycol modifiedand elastomers sold under the trademarks “Hytrel” by E.I. DuPont DeNemours & Company of Wilmington, Del. and “Lomod” by General ElectricCompany, Pittsfield, Mass.

(9) Blends and alloys, including polycarbonate with acrylonitrilebutadiene styrene, polybutylene terephthalate, polyethyleneterephthalate, styrene maleic anhydride, polyethylene, elastomers, etc.and polyvinyl chloride with acrylonitrile butadiene styrene or ethylenevinyl acetate or other elastomers. Blends of thermoplastic rubbers withpolyethylene, propylene, polyacetal, nylon, polyesters, celluloseesters, etc.

Preferably, the cover 11 is comprised of polymers such as ethylene,propylene, butene-1 or hexane-1 based homopolymers and copolymersincluding functional monomers such as acrylic and methacrylic acid andfully or partially neutralized ionomers resins and their blends, methylacrylate, methyl methacrylate homopolymers and copolymers, imidized,amino group containing polymers, polycarbonate, reinforced polyamides,polyphenylene oxide, high impact polystyrene, polyether ketone,polysulfone, poly(phenylene sulfide), acrylonitrile-butadiene,acrylic-styrene-acrylonitrile, poly(ethylene terephthalate),poly(butylene terephthalate), poly(ethelyne vinyl alcohol),poly(tetrafluoroethylene) and their copolymers including functionalcomonomers and blends thereof. Still further, the cover 11 is preferablycomprised of a polyether or polyester thermoplastic urethane, athermoset polyurethane, a low modulus ionomer such as acid-containingethylene copolymer ionomers, including E/X/Y copolymers where E isethylene, X is an acrylate or methacrylate-based softening comonomerpresent in 0-50 weight percent and Y is acrylic or methacrylic acidpresent in 5-35 weight percent. More preferably, in a low spin rateembodiment designed for maximum distance, the acrylic or methacrylicacid is present in 15-35 weight percent, making the ionomer a highmodulus ionomer. In a high spin embodiment, the acid is present in 10-15weigh percent or a blend of a low modulus ionomer with a standardionomer is used.

In the mantle portion 16, the liquid center shell 20, and first andsecond mantle layers 22 and 40 are preferably made of elastomers, suchas thermoset rubber, including polyisoprene, styrene butadiene,polybutadiene and combinations thereof; plastic, such as polypropylene;or thermoplastic elastomeric material such as copolymers ofmethyl-methacrylate with butadiene and styrene, copolymers ofmethyl-acrylate with butadiene and styrene, acrylonitrile styrenecopolymers, polyether-ester, polyether-amide, polyurethane and/or blendsthereof. Most preferably, the first and second mantle layers 22 and 40are made of thermoset rubber or thermoplastic elastomeric materials.

The mantle portion 16 preferably has an outside diameter d3 in the rangeof 80 to 98% of the finished ball diameter D and an inner diameter d1 inthe range of 30 to 70% of the finished ball diameter. Preferably, mantleportion 16 and the liquid center shell 20 have an inner diameter ofapproximately 0.5 to 1.18 inches and, more preferably, an inner diameterof approximately 0.75 to 1.1 inches. Preferably, the mantle portion 16and liquid center shell 20 have an inner diameter of approximately 0.9to 0.95 inches. The first mantle layer 22 preferably has an innerdiameter d2 in the range of 0.55 to 1.45 inches and, more preferably,approximately 0.8 to 1.3 inches. Yet further still, the mantle portion16 has an outside diameter in the range of 1.3 to 1.65 inches and, morepreferably, approximately 1.45 to 1.62 inches.

A golf ball incorporating these measurements can be designed with thevarious attributes discussed below, such as specific gravity, resiliencyand hardness, to provide the desired playing characteristics, such asspin rate and initial velocity. More particularly, by using a liquidcenter shell to surround the fluid center, in an inner sphere, and atleast a first mantle layer, the specific gravities and other propertiescan be tailored to provide optimum playing characteristics. Moreparticularly, by constructing a ball according to these dimensions, thefirst mantle layer 22 is made with a significant volume compared to thefluid center 18. Preferably, the volume of the first mantle layer 22 isgreater than the volume of the fluid center 18. More preferably, thevolume of the first layer 22 is about 2 to 4 times the volume of thefluid center 18. Thus, the properties of the first mantle layer caneffect the playing characteristics of the ball.

The hardness and resiliency of the mantle portion 16 can be varied toachieve certain desired parameters such as spin rate, compression andinitial velocity.

Preferably, the mantle portion 16 has a hardness of approximately 30 to95 Shore C, and more preferably, 45 to 90 Shore C. Still further, themantle portion 16 has a resiliency greater than 40 bashore.

In a most preferred embodiment, the liquid center shell 20 is comprisedof a plastic material having high temperature resistance. The firstmantle layer 22 is comprised of a polybutadiene material that has highspecific gravity for a low spin rate ball and a low specific gravity fora high spin rate ball. The specific gravity of the polybutadienematerial can be varied by adding fillers known to those skilled in theart.

The fluid center 18 can be a wide variety of materials includingsolutions such as air, water, glycerine, paste, foams, oils, watersolutions such as salt in water, corn syrup, salt in water and cornsyrup, or glycol and water. The fluid can also include pastes, colloidalsuspensions, such as clay, barytes, carbon black in water or otherliquid, or salt in water/glycol mixtures; gels, such as gelatin gels,hydrogels, water/methyl cellulose gels and gels comprised of copolymerrubber based materials such a styrene-butadiene-styrene rubber andparaffinic and/or naphthenic oil; or melts including waxes and hotmelts. Hot-melts are materials which at or about normal roomtemperatures are solid but at elevated temperatures become liquid. Thefluid center 18 can also be a reactive liquid system which combine toform a solid. Examples of suitable reactive liquids are silicate gels,agar gels, peroxide cured polyester resins, two part epoxy resin systemsand peroxide cured liquid polybutadiene rubber compositions. It isunderstood by one skilled in the art that other reactive liquid systemscan likewise be utilized depending on the physical properties of theliquid center shell and the physical properties desired in the resultingfinished golf balls.

The fluid center 18 can be varied to modify the performance parametersof the ball, such as the moment of inertia. Preferably, the fluid center18 is comprised of a material that has a high specific gravity for highspin rate golf balls and a material that has a low specific gravity fora low spin rate golf ball. Preferably, the specific gravity of the fluidis below or equal to 1.2 for low specific gravity centers and above 1.2for high specific gravity centers. More preferably, the specific gravityis approximately 1.15-1.2 for low specific gravity centers andapproximately 1.3-1.55 for high specific gravity centers. Still further,the fluid is preferably comprised of a material with a low viscosity fora golf ball having a high spin rate and a material having a highviscosity for a golf ball having a low spin rate. Preferably, theviscosity of the fluid center 18 is less than 100 cps for low viscositycenters and greater than or equal to 100 cps for high viscosity centers.More preferably, the viscosity of the fluid center 18 is less than orequal to 10 cps for low viscosity centers and is between 100 and 1500cps for high viscosity centers. Most preferably, the fluid center 18viscosity is approximately 500 cps for high viscosity centers.

The core 12 is preferably 60 to 95% of the total ball weight and morepreferably, 75 to 86% of the ball weight. As stated above, the weightdistribution within the core 12 can be varied to achieve certain desiredparameters such as spin rate, compression and initial velocity.

For example, by increasing the diameter of the fluid center 18, andincreasing the specific gravity of the mantle portion 16, the weightdistribution of the core 12 is moved toward the outer diameter for alower spin rate ball. In contrast, the diameter of the fluid center 18can be decreased and the specific gravity of the mantle layer 16decreased to move the weight distribution of the ball towards the ballcenter for a high spin rate ball.

Similarly, the specific gravity of the fluid center 18 can be decreasedand the specific gravity of the mantle portion 16 increased for a lowspin rate ball. Alternatively, the specific gravity of the fluid center18 can be increased and the specific gravity of the mantle portion 16decrease for a high spin rate ball.

Various examples of golf ball cores according to the invention are setforth below.

EXAMPLE 1

A core according to the present invention was created having a liquidcenter, a liquid center shell surrounding the liquid and a first mantlelayer surrounding the liquid center shell.

The liquid was a salt, water and corn syrup solution comprised of 40%salt, 30% water and 30% corn syrup. The liquid center had an outsidediameter of approximately 0.965 inches.

The liquid center shell was created from a thermoplastic elastomer. Theliquid center shell had an outside diameter of approximately 1.125inches.

The first mantle layer was created from crosslinked polybutadiene. Thefirst layer had an outside diameter of approximately 1.51 inches.

The core weighed 38.9 g and had a PGA compression of less than 60.

EXAMPLE 2

A core according to the present invention was created having a liquidcenter, a liquid center shell surrounding the liquid and a first mantlelayer surrounding the liquid center shell.

The liquid was a salt, water and corn syrup solution comprised of 40%salt, 30% water and 30% corn syrup. The liquid filled center had anoutside diameter of approximately 0.938 inches.

The liquid center shell was created from polypropylene. The liquidcenter shell had an outside diameter of approximately 1.0625 inches.

The first mantle layer was created from crosslinked polybutadiene. Thefirst mantle layer had an outside diameter of approximately 1.51 inches.

The core weighted 33.4 g and had a PGA compression of approximately 60.

EXAMPLE 3

A core according to the present invention was created having a fluidcenter, a liquid center shell surrounding the fluid and a first mantlelayer surrounding the liquid center shell.

The fluid was air. The fluid center had an outside diameter ofapproximately 0.938 inches.

The liquid center shell was created from polypropylene. The liquidcenter shell had an outside diameter of approximately 1.0625 inches.

The first mantle layer was created from crosslinked polybutadiene. Thefirst mantle layer had an outside diameter of approximately 1.51 inches.

The core weighted 26 g and had a PGA compression of approximately 87.

Turning to the preferred method for making the ball illustrated in FIG.3, the inner sphere is produced by forming the liquid center shell 20 tocreate a central cavity, and filling the cavity with the fluid center18. A first cup is made by compression molding cup material 31,preferably polybutadiene, between a first substantially hemisphericalconcave mold part 32 and a protrusive mold part 34. The protrusive moldpart 34 has a first substantially hemispherical protrusion 35 that facesthe first concave mold part 32. A second cup is then made in the samemanner.

Alternatively, as shown in FIG. 4, the two cups 30 are simultaneouslycompression molded about a single protrusive mold part 36 that has firstand second protrusions 35 and 37. First and second hemispherical molds32 and 33 are positioned opposite each other and protrusive mold part 36is placed between the hemispherical molds 32 and 33.

FIG. 5 shows two concave mold parts 32 and 33 after cups 30 have beenmolded. Each hemispherical cup 30 has a hemispherical cavity 44.Disposed around the cavities 44, the cups 30 have mating surfaces 46,which are substantially flat in this embodiment.

At this point in the process, the inner sphere 13 is placed in the cups30, and the two cups 30 are joined. Cups 30 are preferably kept in theirrespective hemispherical molds 32 and 33 during this step. In oneembodiment, the method for joining the cups 30 is to place adhesive 42between the cups by applying the adhesive to one of the cups 30 as shownin FIG. 5. The cups 30 are then brought together, squeezing the adhesiveevenly across the mating surfaces of the cups 30. The adhesive 42 thensets and bonds the cups 30 to one another. The adhesive is alsopreferably applied such that it bonds the inner sphere 13 to the cups 30by placing adhesive 42 within the cavities. As with the adhesive 42placed between cups, the adhesive 42 placed between the cups 30 and theinner sphere 13 is spread evenly upon joining the cups 30 to oneanother. The hemispherical cavities 44 of the joined cups together forma spherical cavity, occupied by the inner sphere 12.

Another method for joining the cups 30 is to compress them together atan elevated temperature to cause crosslinking between the elastomericcup material of each cup 30. In the embodiment shown in FIG. 4, this maybe achieved by removing protrusive mold part 36, and running thecompression mold through a second cycle, heating and compressing thecups 30 together.

FIG. 6 shows the inner sphere 13 and the cups 30 prior to their beingjoined. In this embodiment, the inner sphere is merely a sphere offrozen fluid 18 that placed between the cups 30, and around which thecups 30 are joined, preferably before the fluid 18 begins to melt.

Once the cups 30 are joined, the cover 11 is formed around the core 12,as seen in FIG. 7. FIG. 8 illustrates a step of compression molding twohalves 70 of a cover 11 around the core 12 in a dimpled mold 68. FIG. 9shows a step of injection molding the cover 11 around the core 12 in adimpled mold 60 with pins 62 that position the core 12 within thedimpled mold 60 and retract before the cover 11 cures completely.

The golf ball of FIG. 7 has been formed by adhesively joining the cups30. Adhesive 42 extends between the cups in the first mantle layer 22,and between each cup 30 and the inner sphere 13. The adhesive 42preferably has an adhesive strength that is greater than the cohesivestrength of the elastomeric cup material. Thus, a ball can bemanufactured that is at least as strong as a ball in which the mantlelayer is made from a single piece of cup material, because the elastomerforming the cups 30 will fail under a lighter load than the adhesive 42.Ideally, the adhesive 42 is flexible in its cured state and has physicalproperties similar to those of the cup material employed.

A preferred adhesive for use with polybutadiene cups 30 is an epoxy,formed by blending low viscosity liquid resins, and formulated to beflexible in its cured state. A suitable epoxy is formed by mixing anapproximately 1:1 volume ratio of about 83 parts by weight of AB-82hardener into 100 parts by weight of Epoxy Resin #1028, both of whichare sold by RBC Industries, Inc. In its liquid state, the epoxy is idealfor use in metering, mixing, and dispensing equipment. This epoxy ispreferably cured at 77° F. for 18 to 24 hours, at 95° F. for 6 hours, at120° F. for 3 hours, or at 150° F. for 1 hour. The cured adhesive'sphysical properties resemble those of elastomeric urethane. It exhibitsan Izod impact strength of 5.50 ft. lbs./in. of notch, a tensilestrength at 25° C. of 2,200 psi, a compressive strength at 25° C. of6,000 psi, and a shore D hardness of 45. Preferably, the shore D of thecured adhesive is within 20 shore D of the hardness of the elastomericcup material.

Other preferred adhesives are those adhesives containing cyanoacrylate.

FIGS. 10 and 11 show alternative embodiments of cups 48 and 54. Insteadof having flat mating surfaces, cups 48 and 54 have nonplanar matingsurfaces 50 and 52, and 56 and 58. These surfaces 50 and 52, and 56 and58 each have a circular pattern of ridges that is preferably symmetricalabout the cavity 44 of each cup 48 and 54; the patterns shown areconcentric with the cups 48 and 54. In ball 53, surface 58 has a tonguethat engages a groove of surface 56. In the finished golf balls 47 and53, nonplanar surfaces 50 and 52 are arranged to mesh with each other,as are nonplanar surfaces 56 and 58. These nonplanar mating surfaces 50and 52 are preferably formed by molding the cups 48 or 54 withprotrusive mold parts that have nonplanar surfaces surrounding theirprotrusions, such as the protrusive mold part 36 with nonplanar surfaces64 and 66, as shown in FIG. 4.

The liquid center shell and mantle layers in the mantle portion 16 ofthe golf ball with nonplanar mating surfaces retain more of theproperties of the elastomers that form the cups, when the cups areforced in shear with respect to each other, as compared to a golf ballwith flat mating surfaces. Nonplanar mating surfaces are thusadvantageous when an adhesive is used that has an adhesive strengthlower than the cohesive strength of the elastomeric cup material. Thisis because the meshed portions of the cups 48 and 54 aid in resistingshearing forces between the two cups 48 and 54.

While it is apparent that the illustrative embodiments of the inventionherein disclosed fulfills the objectives stated above, it will beappreciated that numerous modifications and other embodiments may bedevised by those skilled in the art, for example, a series ofprogressively larger diameter cups can be formed and joined by themethods disclosed. Therefore, it will be understood that the appendedclaims are intended to cover all such modifications and embodimentswhich come within the spirit and scope of the present invention.

What is claimed:
 1. A method of making a ball, comprising: a) forming aninner sphere by forming an outer shell with a fluid mass center; b)forming a plurality of core parts from elastomeric material; c)arranging and adhesively joining the core parts around the inner spherewith a flexible adhesive and then crosslinking the core parts to eachother by compressing them together at an elevated temperature to form asubstantially spherical core; d) molding a cover around the assembledcore, wherein the elastomeric material has a cohesive strength and theadhesive has an adhesive strength that is stronger than the cohesivestrength.
 2. The method of claim 1, further comprising molding nonplanarmating surfaces on the core parts, wherein the core parts comprisesmeshing the mating surfaces.
 3. The method of claim 1, wherein formingthe inner sphere comprises freezing a sphere of a fluid.
 4. The methodof claim 1, wherein the forming of the core parts comprises compressionmolding the core parts.
 5. The method of claim 1, wherein: a) theforming of the plurality of core parts comprises forming first andsecond substantially hemispherical cups having cavities; and b) thearranging of the core parts comprises placing the inner sphere in saidcavities.
 6. The method of claim 5, wherein the forming of the cupscomprises forming nonplanar corresponding mating surfaces on the cupsadjacent the cavities.
 7. The method of claim 6, wherein arranging thecore parts comprises meshing the mating surfaces.
 8. The method of claim7, wherein the forming of the mating surfaces comprises forming patternsin the mating surfaces that are symmetrical about the cavities of thecups.
 9. The method of claim 8, wherein the forming of the patternscomprises forming the mating surfaces into concentric ridges.
 10. Themethod of claim 1, wherein the elastomeric material is selected from thegroup consisting of thermoset rubber, including polyisoprene, styrenebutadiene, polybutadiene and combinations thereof.
 11. The method ofclaim 10, wherein after arranging and adhesively joining the core partsaround the inner sphere the method further includes separately moldingtwo substantially hemispherical cups from elastic material for joiningover the core.
 12. The method of claim 1, wherein the forming of thecore parts comprises applying hat and pressure to the core parts fromthe elastomeric material on opposite sides of a single mold part.